I recall working at a place which was transitioning from CFEngine to Puppet. None of the fancy "promise theory" was used; sysadmins did whatever was necessary t

I recall working at a place which was transitioning from CFEngine to Puppet. None of the fancy "promise theory" was used; sysadmins did whatever was necessary to get things configured, and that was it. As a result, Puppet was a breath of fresh air because, while it was no more intelligent about describing machines, it was certainly more direct about changing them. To me, CFEngine has been behind the pack for a long time. I use Nix now, and right now in order to be ahead of the pack, a configuration manager needs not just declarative configuration, but atomic upgrades and rollbacks, dry-run builds and upgrades, service isolation, and service discovery or meshing.